This invention relates to improved flail feedout means for mowing and trimming devices used to trim grass, weeds and other vegetation, of the rotary type equipped with flexible cord-like flails formed of generally cylindrical fibers. Grass and weed cutters of this general type are now widely used. Examples are described in U.S. Patents: REBER, U.S. Pat. No. 3,664,102; BALLAS et al., U.S. Pat. No. 3,826,068; MIZUNO et al., U.S. Pat. No. 4,020,552; BALLAS et al., U.S. Pat. No. 4,035,912; in my U.S. Pat. No. 4,097,991 co-pending U.S. patent application Ser. No. 881,193. Such devices are available on the market having automatic flail feedout mechanisms which respond to a bump on the ground intentionally applied by the operator. Such mechanisms usually consist of a dog or friction clutch located between a spool of flail and the case thereabout through which the flail is fed. By bumping an extension of the spool on the ground, the friction clutch is disengaged for a length of time dependent on the duration of the bump. The dog clutch released by the bump then abruptly engages at the next opportunity to feedout flail in segment lengths which are related to the engagement points of the dog clutch. Such dog clutches have outwardly extending ribs which engage inwardly extending abutment tangs and therefore depend upon a skillful bump when it is desired that they move only one segment. However, friction within the device and overzealous bumping can result in two or more line segments being fed out, especially when the device has been in use and the corners on the ribs and tangs have worn so that positive engagement is no longer assured. The abrupt operation of the dog clutch insures that the wear takes place. Therefore, there has been a need for a feedout mechanism which automatically feeds out a predetermined length of flail per bump, which does not lose this capability quickly with use, and which is easy to construct and maintain.